Thermoplastic composition



Patented Sept. I 14, 19 2 6.

UNITED STATES PATENT OFFICE.

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THERMOPLASTIC COl'lIPOSITION'.

Ho Drawing. 0riginal applicationifiled December 1, 1922, Serial No.604,415, Divided and this application filed October 2, 1924. Serial No.741,244.

' In the manufacture of shoe stifi'eners and articularly those which areemployed for orming the toe box of a shoe, it is desirable to employ afibrous foundation and to saturate the same with or incorporate thereina thermo-plastic composition which gives stifiness and resiliency to theblank when cold,

and which imparts to the blank a water-re.

sistant characteristic.

It is highly desirable that the thermo-plastic composition should be ofsuch nature that it Will soften at a relatively low temperature so. thatthe blank may be rendeied limp and flexible, and set rapidly when cooledso that the blank may retain the shape in which it is molded by thepullingover or lasting operation to which the partially finished shoe issubjected. In addition,

the blank when cold should be tough and "yet hard and resilient so as towithstand the pressures to which the shoe is subjected in wear andspring back into shape if momentarily deflected or compressed.

In the manufacture of sheet material from which such'blanks are made,particularly when the fibrous foundation is to be saturated with thethermo-plastic composition while the latter is in a molten condition,the stiffening agent shouldpossess a relatively high degree of fluidityor penetrability so as to thoroughly impregnate and saturate the fibrousfoundation. Moreover the stiflening agent should be of suchcharacterthat it will not soften when subjected to body or solar heat.Moreover the shoe stiff ener itself should be more or less waterproof orwater-repellent. Again it is desirable that the stiffening agent shouldpossess more or less of a cementitious quality. so that such stiifeninagent as is exuded during the lasting or pufiing-over operation mayserve to bind the lining and upper of the shoe to the blank. It isdesirable for use in shoes, made from light-colored material asdistinguished from black material, that'the thermo-plastic compositionshould be light in After, rolonged experimentation, I have discover-ethat, by combining certain ingredients, I am able to provide athermoplastic or stiffening composition with which the fibrousfoundation may be saturated or treated to produce a box toe having thedesirable characteristics hereinabove referred found in practice to giveexcellent results.

4,400 pounds of rosin and 700 pounds of copal (which constitute the acidresin of the final product), together with 115 pounds of hydrated lime(the base) are placed in a ket tle, melted and thoroughly stirredtogether to form a substantially homogeneous mass. During the heatingand fusing operation, the lime reacts with a portion of the acids of theresins to form resin-Soaps, such soaps forming however a relativelysmall portion of the resulting product. By heating the copal and therosin together, the mass is made fluid at a relatively lower temperaturethan would be required if the copal were heated separately. Copal breaksdown or decomposes to some e'xtent'at a temperature of about-300 F.,certain volatile matters being evolved at this temperature; but, whenmixed with rosin as previously stated, the copal decomposes at a lowertemperature and is soluble in the fluid molten rosin. To the fluid massI now add 1,000 arts ofasuitable-hard wax, such as carnau a, candellila,shellac wax or Montan wax, preferably Montan wax because of its greatercheapness.

The wax may be first melted before being mixed with the first-mentionedmass, or it, h

may be added in the cold and melted while being thoroughly stirred intothe said firstmentioned mass. After a homogeneous mixture has beenproduced, I now add a rela-' I tively small quantity (say 150 pounds) ofa drying oil. For this purpose, I preferably emplo China wood oil whichhas been heated an polymerized to an incipient gel form.

The mass is now ready to be used for treatment of the fibrousfoundation.

The fibrous foundation itself may be a sheet of wool felt or mixedcotton and wool felt, or it may consist of a'sheet of paper feltmanufactured by the aid of a paper machine. In the latter case, thethermo-plastic composition may by suitable procedure be incorporatedwith the pulp prior to theformation of the sheet. Ordinarily, however,

the sheet is formed, and, when dry, is passed through a bath of themolten thermo-plastic composition so as to be thoroughly impregnated orsaturated therewith. After the sheet has been thus saturated orimpregnated, it is now out into blanks of appropriate size and shape, e.g. for use as box toes, which blanks are skive'd and preferablycalendered by heated rolls.

Rosin and copal when cold are brittle or friable and do not possess thatdegree of toughness which should characterize a thermo-plasticcomposition or stiffening agent for the use herein described. Byutilizing therewith, a base for the formation of resin soaps, and adrying oil, there is imparted to the thermo-plastic composition arelatively high degree of toughness without adversely affecting therelative resiliency of the fin-- ished box toe. The wax, whichconstitutes about one-sixth, more 'or less, of the entire mass, is addedto increase the hardness of the thermo-plastic composition, but inaddition it greatly increases thdpenetrability or fluidity of the massso that it will thoroughly saturate the fibrous foundation. Athermo-plastic composition as thus described softens sufficiently torender the blank limpand moldable at a temperature of from 180 to 200F., so that, when the box-toe blank has been assembled with the leatherupper, the blank may be rendered limp and flexible by the application ofheat at a temperature which is not injurious to the leather.

One of the highly desirable characteristics of the thermo-plasticcomposition herein described is that it has a relatively shortmelting-point lag, so that it sets very quickly when cooled, and remainsrigid until it-is heated to a relatively definite temperature.

A useful procedure, in incorporating the base with the acid resins, isto mix the powdered basewith a considerable amount of powdered orcrushed acid resin before adding it to'the molten resin, since thisprevents the formation of lumps which would take place if the basewereadded in amass.

This application is a division of my copending application Serial No.604,415, filed December 1, 1922.

VVh'at I claim is:

1. A thermoplastic composition of matter, suitable as a stiffening agentfor fibrous parts of shoes, comprising acid resin, hard wax, resin soapand drying oil.

2. The herein decribed process of produc' ing a thermo-plasticcomposition for use in the manufacture of shoe stiifeners,- whichcomprises melting acid resin, adding a base thereto for reactiontherewith and the formation of resin soap, adding a wax to the moltenmass, and then incorporating a drying oil to such mass while the /latteris molten.

I 3. The herein described process of producing a thermo-plasticcomposition for use in the manufacture of shoe stifiene'rs, whichcomprises melting acid resin, adding thereto a base mixed with powderedacid resin, for the formation of resin soap, adding a hard wax to saidmass, and then incorporating China wood oil to the molten mass.

In testimony whereof I have aflixed my signature.

CHARLES E. SWETT.

